Surface acoustic wave sensor assembly

ABSTRACT

A sensor assembly that includes a surface acoustic wave (SAW) sensor. The SAW sensor is adapted to measure a first environmental condition in response to receiving an RF signal. The SAW sensor includes a substrate having a layer of piezoelectric material. The SAW sensor further includes a interdigitated transducer (IDT) formed on the piezoelectric material. The IDT includes two comb-shaped electrodes having interlocking conducting digits in a first arrangement. The interlocking conducting digits in the first arrangement generates a first signal modulation of an RF signal received by the first IDT. The first signal modulation identifies the first SAW sensor.

TECHNICAL FIELD

Some embodiments of the present disclosure relate, in general, to asensor device having a surface acoustic wave (SAW) sensor assembly tomeasure an environmental condition of an environment.

BACKGROUND

Surface acoustic waves (SAWs) are sound waves that travel parallel tothe surface of an elastic material. The general mathematical discussionof SAW was first reported by Lord Rayleigh in 1855, but the applicationin electronic devices was not exploited until 1965 by White and Voltmerutilizing interdigital transducer on piezoelectric materials. SAWs areused in a electronic devices, particularly RF/IF filters. Thetransduction from electrical energy to mechanical energy (in the form ofSAWs) is accomplished through the use of piezoelectric materials.Piezoelectric materials are materials that have the ability to generateinternal electrical charge from mechanical stress as well as internallygenerate mechanical strain in response to an applied electric field. ASAW transducer is often used on a surface of piezoelectric materials toconvert electrical energy to mechanical energy (e.g., SAWs) as well asconvert SAWs into electrical energy. SAW devices may use SAWs inelectronic components to provide a number of different functions,including delay lines, filters, resonators, correlators, converters,sensors, and the like. SAW devices can be disposed on wafers to performtheir respective functions.

SUMMARY

Some embodiments described herein cover a sensor device including anintegrated sensor assembly having a surface acoustic wave (SAW) sensordisposed on a substrate having at least a layer of a piezoelectricmaterial. The SAW sensor may be adapted to measure an environmentalcondition based on detection of SAW properties responsive to receivingan incoming radio frequency (RF) signal. The SAW sensor may include aninterdigitated transducer (IDT) formed on the piezoelectric material.The IDT may generate a SAW based on the environmental conditionresponsive to receiving the incoming RF signal. The SAW sensor mayinclude one or more SAW reflectors that communicates with the IDT. TheSAW sensor may include another IDT to receive the SAW wave and generatean outgoing RF signal. The SAW sensor assembly may further include an RFantenna and matching circuitry. The matching circuitry may be connectedto the RF antenna and the IDT. The SAW sensor, the RF antenna, and thematching circuitry may be integrated with each other on thepiezoelectric material.

In further embodiments, the sensor assembly may include a second IDTthat receives the SAW from the first IDT and generates an oscillatingpotential associated with an acoustic frequency of the received SAW.This oscillating potential may include information associated with ameasured environmental condition across a region of the surface of thepiezoelectric substrate or piezoelectric layer. The sensor assembly mayinclude a second RF antenna and second matching circuitry to output anoutgoing RF signal associated with the oscillating potential.

In example embodiments, a method is disclosed for fabricating a sensordevice. The method may include fabricating an integrated sensor assemblyby depositing a first conductive structure onto a substrate having atleast a layer of a piezoelectric material, where the first conductivestructure forms a radio frequency (RF) antenna. The method may furtherinclude depositing a second conductive structure onto the piezoelectricmaterial, where the second conductive structure forms matching circuitrythat is connected to the RF antenna. The method may further includedepositing a third conductive structure onto the piezoelectric material,where the third conductive structure forms an interdigitated transducer(IDT) connected to the RF antenna, wherein the IDT is a component of asurface acoustic wave (SAW) sensor. The method may further includedepositing a fourth conductive structure onto the piezoelectricmaterial, where the fourth conductive structure forms at least one of a)one or more SAW reflectors or b) a second IDT. The first conductivestructure, second conductive structure, third conductive structureand/or fourth conductive structure may be formed together in a singledeposition operation in some embodiments.

In some embodiments, the sensor assembly may include a SAW sensoradapted to measure an environmental condition responsive to receiving anincoming RF signal. The SAW sensor may include at least a layer of apiezoelectric material disposed on a base substrate. The SAW sensor mayfurther include a first IDT formed on the piezoelectric substrate, wherethe first IDT operates at a base resonant frequency. The SAW sensor mayinclude a dielectric coating with a thickness or material associatedwith a shift in the base resonant frequency, where the first IDT withthe dielectric coating has an adjusted resonant frequency.

In example embodiments, a method is disclosed for fabricating a sensorassembly. The method may begin with fabricating a SAW sensor bydepositing a conducting layer onto a piezoelectric substrate, where theconducting layer forms an interdigitated transducer (IDT) of the SAWsensor. The IDT has a base resonant frequency based, for example, on thepitch between digits in the IDT. The method may continue with tuning aresonant frequency of the IDT by depositing a dielectric coating havinga thickness of a material on the conducting layer, where at least thethickness or the material is associated with a shift in the baseresonant frequency, where the IDT with the dielectric coating has anadjusted resonant frequency.

In other embodiments, the sensor assembly may include one or multipleSAW sensors adapted to measure an environmental condition responsive toreceiving an incoming RF signal. A first SAW sensor may include asubstrate having at least a layer of a piezoelectric material and afirst IDT formed on the piezoelectric material. The first IDT mayinclude two comb-shaped electrodes comprising interlocking conductingdigits disposed in a first arrangement. The interlocking conductingdigits in the first arrangement generates a signal modulation of asignal received by the IDT. The signal modulation identifies the SAWsensor.

In other embodiments, the sensor assembly may include a SAW sensordisposed on a substrate having at least a layer of a piezoelectricmaterial. The SAW may be adapted to measure an environmental conditionof an environment responsive to receiving an incoming RF signal. The SAWsensor may include an IDT formed on the piezoelectric material. The IDTgenerates a SAW based on the environmental condition responsive toreceiving the incoming RF signal. The SAW sensor may further include acollection of SAW reflectors that have a spatial arrangement that causesthe SAW reflected from the SAW reflectors propagating from the SAWreflectors back to the IDT to have a signal modulation that identifiesthe SAW sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that differentreferences to “an” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone.

FIG. 1 illustrates a simplified top view of an example processingsystem, according to aspects of the present disclosure.

FIG. 2 is a top, perspective view of a sensor device includingintegrated SAW sensor assemblies, according to aspects of thedisclosure.

FIGS. 3A-B depict various embodiments of SAW sensor assemblies,according to aspects of the disclosure.

FIG. 4 is a flow chart of a method for fabricating a SAW sensorassembly, according to aspects of the disclosure.

FIGS. 5A-B are top, perspective views of various embodiments of SAWsensors with dielectric coatings, according to aspects of thedisclosure.

FIG. 6 is a graph depicting a frequency shift in base resonant frequencyof an SAW sensor, according to aspects of the disclosure.

FIG. 7 is a top perspective view of a sensor device, according toaspects of the disclosure

FIG. 8 is a flow chart of a method for fabricating a SAW sensorassembly, according to aspects of the disclosure.

FIGS. 9A-C depict various embodiments of electrode arrangements of IDTsof a SAW sensor, according to aspects of the disclosure.

FIGS. 10A-B depict various spatial arrangements of SAW reflectors of SAWsensors, according to aspects of the present disclosure.

FIGS. 11-14 are top, perspective views of various embodiments of sensordevices, according to aspects of the disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure provide a sensor device includinga SAW sensor assembly and related methods for fabricating a SAW sensorassembly. The SAW sensor assembly may include conductive elements suchas antennas, circuitry, and/or interdigitated transducers (IDTs)disposed on a substrate having at least a layer of a piezoelectricmaterial. The SAW sensor assembly may be formed, for example, on apiezoelectric substrate or on another type of substrate such as asemiconductor substrate that has a piezoelectric layer thereon. The SAWsensor receives incoming RF signals and generates SAWs to measureenvironmental conditions such as pressure and temperature of anenvironment (e.g., surface of the piezoelectric substrate orpiezoelectric layer). Various disclosed embodiments provide a way tomeasure environmental conditions passively (e.g., without active devicessuch as a power supply), make measurements over a surface area of apiezoelectric substrate or piezoelectric layer, fine tune SAW sensors,and/or distinguish between various SAW sensors of a sensor assembly.

Various embodiments may be or employ a device having a sensor assemblythat includes a SAW sensor disposed on a substrate having at least alayer of a piezoelectric material (e.g., on a piezoelectric substrate oron a piezoelectric layer disposed on a substrate) and that is adapted tomeasure an environmental condition of an environment responsive toreceiving an incoming RF signal. The SAW sensor may include an antenna,matching circuitry, and an interdigitated transducer (IDT) disposed onthe surface of the piezoelectric material. The SAW sensor may generate aSAW to measure the environmental condition without using activecircuitry (e.g., CMOS devices powered by a battery). The antenna,matching circuitry, and interdigitated transducer may be integrated withone another on the piezoelectric material.

In an example, a sensor device includes an integrated sensor assemblyhaving a SAW sensor disposed on a piezoelectric substrate. The SAWsensor may be adapted to measure an environmental condition of anenvironment responsive to receiving an incoming radio frequency (RF)signal. The SAW sensor may include an IDT formed on the piezoelectricsubstrate. The IDT may generate a SAW based on the environmentalcondition (e.g., having at least one of an amplitude, a frequency, atime delay, a phase or a wavelength that is dependent on theenvironmental condition) responsive to receiving the incoming RF signal.The SAW sensor may include one or more SAW reflectors that reflect theSAW back to the IDT. The IDT may then generate a new outoing RF signalbased on the reflected SAW that is received. For example, the IDT maygenerate an oscillating electrical potential associated with an acousticfrequency of the reflected SAW. This oscillating potential may includeinformation associated with a measured environmental condition across aregion of the surface of the piezoelectric material. The SAW sensorassembly may further include an RF antenna and matching circuitryattached to the first IDT. The matching circuitry may be connected tothe RF antenna and the first IDT. The SAW sensor, the RF antenna, andthe matching circuitry may be integrated with each other on thepiezoelectric material.

In some embodiments, the sensor assembly may include a SAW sensor havingtwo IDTs that are separated by a surface of a piezoelectric substrate ora piezoelectric layer on a substrate. A first IDT may be used to receivean incoming RF signal and generate a SAW that is passed along thesurface of the piezoelectric substrate or piezoelectric layer to theother IDT. The other IDT may receive the SAW and generate an oscillatingpotential associated with the acoustic frequency of the SAW. Thisoscillating potential may include information associated with a measuredenvironmental condition (e.g., temperature, pressure, or the like),where the environment includes the region between the IDTs. Each IDT maybe coupled to an RF antenna through matching circuitry.

In an example, in addition to or instead of including one or morereflectors, the SAW sensor may include two IDTs (one to generate a SAWand the other to receive the SAW and generate a new outgoing RF signaltherefrom). The additional IDT generates an oscillating electricalpotential associated with an acoustic frequency of the received SAW.This oscillating potential may include information associated with ameasured environmental condition across a region of the surface of thepiezoelectric material (e.g., the piezoelectric substrate orpiezoelectric layer). In embodiments that include a second IDT, the SAWsensor assembly may further include a second RF antenna to output thenew outgoing RF signal and second matching circuitry coupled to thesecond RF antenna and the additional IDT. The second RF antenna and thesecond matching circuitry may be integrated with each other and with theSAW sensor, the RF antenna and the matching circuitry on thepiezoelectric material.

In example embodiments, a method is disclosed for fabricating a sensordevice. The method may include fabricating an integrated sensor assemblyby depositing a first conductive structure onto a substrate having atleast a layer of a piezoelectric material, where the first conductivestructure forms a radio frequency (RF) antenna. The method may furtherinclude depositing a second conductive structure onto the piezoelectricmaterial, where the second conductive structure forms matching circuitrythat is connected to the RF antenna. The method may further includedepositing a third conductive structure onto the piezoelectric material,where the third conductive structure forms an interdigitated transducer(IDT) connected to the RF antenna, wherein the IDT is a component of asurface acoustic wave (SAW) sensor. The method may further includedepositing a fourth conductive structure onto the piezoelectricmaterial, where the fourth conductive structure forms at least one of a)one or more SAW reflectors or b) a second IDT. The first conductivestructure, second conductive structure, third conductive structureand/or fourth conductive structure are formed together in a singledeposition operation in some embodiments. Alternatively, multipledeposition operations may be performed, with each deposition operationsforming one or more of the first conductive structure, the secondconductive structure, the third conductive structure and the fourthconductive structure. These conductive structures may each be planarconductors in embodiments. By fabricating a sensor device having all ofthe components in one integrated device enables the use of a smallersensor device that in turn can reduce manufacturing cost, time, andreduce the required number of manufacturing steps.

In embodiments, the sensor assembly includes a SAW sensor having a firstIDT disposed on a piezoelectric material that operates at a baseresonant frequency. The first IDT may include a dielectric coating witha thickness and/or material associated with a shift in the base resonantfrequency, where the first IDT with the dielectric coating has anadjusted resonant frequency. In a further embodiment, the sensorassembly may include various SAW sensors, each having IDTs withdielectric coatings of different thicknesses and/or materials that causeeach respective IDT to have a different adjusted resonant frequency.Each unique frequency may allow a reader to receive outgoing RF signalsgenerated by the different SAW sensors and to distinguish between thoseoutgoing RF signals. This enables a sensor wafer to be manufactured thatincludes multiple (e.g., 5-20 or more) SAW sensors to be disposed on thesame sensor wafer. Signals generated by each of the SAW sensors on thesensor wafer may be received by the reader. The reader (or a controllerconnected thereto) may then determine which of the SAW sensors generatedeach particular outgoing RF signal based on the frequency of thatoutgoing RF signal. This enables the detector and/or controller todetermine different environmental conditions across different locationsof the sensor wafer.

In example embodiments, a method is disclosed for fabricating a sensorassembly. The method may begin with fabricating a SAW sensor bydepositing a conducting layer onto a piezoelectric substrate, where theconducting layer forms an interdigitated transducer (IDT) of the SAWsensor. The IDT has a base resonant frequency based, for example, on thepitch between digits in the IDT. The method may continue with tuning aresonant frequency of the IDT by depositing a dielectric coating havinga thickness of a material on the conducting layer, where at least thethickness or the material is associated with a shift in the baseresonant frequency, where the IDT with the dielectric coating has anadjusted resonant frequency.

In some embodiments, the sensor assembly has a SAW sensor that includesan IDT having two comb-shaped electrodes including interlockingconducting digits in an arrangement. The arrangement of interlockingconducting digits may generate a signal modulation of a signal passedthrough the IDT. This signal modulation may identify the SAW sensor. Inaddition, or in the alternative, the sensor assembly may have a SAWsensor that includes an IDT and a collection of SAW reflectors that havea spatial arrangement that causes the reflected SAWs to have a signalmodulation that identifies the SAW sensor.

In an example, the sensor assembly may include multiple SAW sensorsadapted to measure an environmental condition responsive to receiving anincoming RF signal. A first SAW sensor may include a piezoelectricsubstrate and a first IDT formed on the piezoelectric substrate. Thefirst IDT may include two comb-shaped electrodes comprising interlockingconducting digits disposed in a first arrangement. The interlockingconducting digits in the first arrangement generates a signal modulationof a signal received by the IDT. The signal modulation identifies theSAW sensor. A second SAW sensor may include a second IDT formed on thepiezoelectric substrate (or on a different piezoelectric substrate). Thesecond IDT may include two comb-shaped electrodes comprisinginterlocking conducting digits disposed in a second arrangement. Theinterlocking conducting digits in the second arrangement generates asecond signal modulation of a signal received by the second IDT. Thesecond signal modulation identifies the second SAW sensor. Thus, RFsignals output by the first and second SAW sensors may be identifiedbased on their associated signal modulations. This enables a sensorwafer to be manufactured that includes multiple (e.g., 5-20 or more) SAWsensors to be disposed on the same sensor wafer. Signals generated byeach of the SAW sensors on the sensor wafer may be received by thereader. The reader (or a controller connected thereto) may thendetermine which of the SAW sensors generated each particular RF signalbased on the frequency of that RF signal. This enables the detectorand/or controller to determine different environmental conditions acrossdifferent locations of the sensor wafer.

Any of the above disclosed embodiments may be combined. For example, asensor wafer may include a first SAW sensor with a first dielectriccoating, a first arrangement of digits of an IDT and/or a firstarrangement of reflectors and a second SAW sensor with a seconddielectric coating, a second arrangement of digits of an IDT, and/or asecond arrangement of reflectors. The first and second SAW sensors mayoptionally each be part of respective integrated sensor assemblies thatinclude respective antennas and matching networks. In some embodiments,the integrated sensor assemblies of multiple SAW sensors are included ona shared piezoelectric substrate or other substrate with a piezoelectriclayer disposed thereon.

These and similar embodiments provide a number of advantages andimprovements in the field of fabrication and signal processing of sensorassemblies such as SAW sensors and sensor wafers that include one ormore SAW sensors disposed on the sensor wafer. These advantages includeimprovements in SAW sensor assemblies such as improved SAW sensorperformance, broader applicable use of SAW sensors, increased signaldifferentiation between SAW sensors, and reduced manufacturing costs andfabrication complexities of SAW sensors.

Sensor performance may be improved, for example, by a sensor assemblythat uses passive circuitry (e.g., SAW sensors). The passive circuitryallows the measurement of environmental conditions at more extremelevels (e.g., high temperatures and pressures) by not being restrictedto an active device's specification limitations. Broader applicable useof SAW sensors may be achieved, for example, by using IDTs the arecoupled to unique antennas. IDTs coupled to unique antennas can be usedto measure environmental conditions across a wider environment bysending SAW between IDTs disposed across a broad area of a piezoelectricsubstrate. Increased signal differentiation between SAW sensors may beachieved, for example, by generating a sensor assembly with SAW sensorsthat are tuned to operate at different frequencies by applying adielectric coating with a unique thickness or material. Alternatively,or additionally, the SAW sensors may generate unique signal modulationson signals passing through each respective SAW sensor. The signalmodulation may be generated using arrangements of interlockingconducting digits of the IDT electrode and/or spatial arrangements ofSAW reflectors.

FIG. 1 illustrates a simplified top view of an example processing system100, according to aspects of the present disclosure. The processingsystem 100 includes a factory interface 91 to which a plurality ofsubstrate cassettes 102 (e.g., front opening pods (FOUPs) and a sidestorage pod (SSP)) may be coupled for transferring substrates (e.g.,wafers such as silicon wafers) into the processing system 100. The FOUP,SSP, and other substrate cassettes may together be referred to herein asstorage locations. In some embodiments, one or more of the substratecassettes 102 include, in addition to or instead of wafers to beprocessed, one or more sensor wafers 110 having SAW sensor assembliesdisposed thereon or integrated therein. The SAW sensor assemblies of thesensor wafers 110 may be used to measure environmental conditions (e.g.,temperature, pressure, or the like) of an environment. For example, thesensor wafers 110 may be used to measure an environmental conditionwithin one or more processing chambers 107 and other compartments andchambers as will be discussed. The factory interface 91 may alsotransfer the sensor wafers 110 into and out of the processing system 100using the same functions for transferring wafers to be processed and/orthat have been processed, as will be explained.

The processing system 100 may also include first vacuum ports 103 a, 103b that may couple the factory interface 91 to respective stations 104 a,104 b, which may be, for example, degassing chambers and/or load locks.Second vacuum ports 105 a, 105 b may be coupled to respective stations104 a, 104 b and disposed between the stations 104 a, 104 b and atransfer chamber 106 to facilitate transfer of substrates into thetransfer chamber 106. The transfer chamber 106 includes multipleprocessing chambers 107 (also referred to as process chambers) disposedaround the transfer chamber 106 and coupled thereto. The processingchambers 107 are coupled to the transfer chamber 106 through respectiveports 108, such as slit valves or the like.

The processing chambers 107 may include one or more of etch chambers,deposition chambers (including atomic layer deposition, chemical vapordeposition, physical vapor deposition, or plasma enhanced versionsthereof), anneal chambers, and/or the like. The processing chambers 107may include chamber components such as a showerhead or a chuck (e.g.,electrostatic chuck), for example.

In various embodiments, the factory interface 91 includes a factoryinterface robot 111. The factory interface robot 111 may include a robotarm, which may be or include a selective compliance assembly robot arm(SCARA) robot, such as a 2 link SCARA robot, a 3 link SCARA robot, a 4link SCARA robot, and so on. The factory interface robot 111 may includean end effector on an end of the robot arm(s). The end effector may beconfigured to pick and handle specific objects, such as wafers. Thefactory interface robot 111 may be configured to transfer objectsbetween substrate cassettes 102 (e.g., FOUPs and/or SSP) and stations104 a, 104 b (e.g., which may be load locks).

The transfer chamber 106 includes a transfer chamber robot 112. Thetransfer chamber robot 112 may include a robot arm with an end effectorat an end of the robot arm. The end effector may be configured to handleparticular objects, such as wafers, edge rings, ring kits, and/or sensorwafers 110. The transfer chamber robot 112 may be a SCARA robot, but mayhave fewer links and/or fewer degrees of freedom than the factoryinterface robot 111 in some embodiments.

The processing system may include one or more RF antennas 129 in theprocessing chambers 107. The RF antennas 129 may be disposed on orwithin the walls of the processing chambers 107 in embodiments. The RFantennas may be disposed within chamber components in some embodiments.For example RF antennas 129 may be disposed within a chuck (e.g., anelectrostatic chuck) or a showerhead of a processing chamber. One ormore RF antennas 129 may additionally or alternatively be disposedwithin the transfer chamber 106, within a load lock (e.g., load locks104 a, 104 b), within the FI 101 and/or within the cassettes 102.

The RF antennas 129 may be communicatively coupled to the SAW sensorassemblies on a sensor wafer 110. For example, RF signals can be sentfrom RF antennas 129 to SAW sensor assemblies on a sensor wafer 110 anda return signal can be generated by the SAW sensor assemblies andreceived by the same RF antenna or another RF antenna 129. The returnsignal may include information indicative of a measurement of anenvironmental condition of an environment within a processing chamber,load lock, transfer chamber, and so on (e.g., on the surface of the SAWsensor assembly). The RF antennas may be connected to transceivers thatgenerate RF signals and/or that receive RF signals. In some embodiments,one or more RF antennas associated with a processing chamber areconnected to an RF transmitter and one or more RF antennas associatedwith the processing chamber are connected to an RF receiver. The sensorwafers may not include any power components (e.g., any batteries), andmay instead be powered by the received RF signals generated by the RFantennas 129. Thus, the sensor wafers may be passive devices.

A controller 109 may control various aspects of the processing system100 and may be communicatively coupled to RF antennas 129. Thecontroller 109 may be and/or include a computing device such as apersonal computer, a server computer, a programmable logic controller(PLC), a microcontroller, and so on. The controller 109 may include oneor more processing devices such as a microprocessor, central processingunit, or the like. More particularly, the processing device may be acomplex instruction set computing (CISC) microprocessor, reducedinstruction set computing (RISC) microprocessor, very long instructionword (VLIW) microprocessor, or a processor implementing otherinstruction sets or processors implementing a combination of instructionsets. The processing device may also be one or more special-purposeprocessing devices such as an application specific integrated circuit(ASIC), a field programmable gate array (FPGA), a digital signalprocessor (DSP), network processor, or the like.

Although not illustrated, the controller 109 may include a data storagedevice (e.g., one or more disk drives and/or solid state drives), a mainmemory, a static memory, a network interface, and/or other components.The controller 109 may execute instructions to perform any one or moreof the methodologies and/or embodiments described herein. Theinstructions may be stored on a computer readable storage medium, whichmay include the main memory, static memory, secondary storage and/orprocessing device (during execution of the instructions). For example,the controller 109 may execute the instructions to activate one or moreRF antennas 129 that are located within the different storage locations,the factory interface 91, the load lock or stations 104 a, 104 b, thetransfer chamber 106, and/or any of the processor chambers 107. Thecontroller 109 may then receive return RF signals generated by SAWsensor assemblies on the sensor wafer 110, and may analyze the receivedRF signals. Each of the SAW sensor assemblies may be configured tomeasure a particular environmental property, such as pressure,temperature, plasma power, and so on, and to output an RF signalindicative of a measurement of the particular environmental property.Additionally, multiple different SAW sensor assemblies on a sensor wafermay be configured to measure different environmental properties. Thecontroller 109 may receive the RF signals and determine the measurementvalues (e.g., of amplitude, phase, frequency and/or time-delay) for theenvironmental property (or properties) that was measured based on thereceived RF signals.

In some embodiments, a single sensor wafer 110 includes multiple SAWsensor assemblies that are tuned to different frequencies and/or thatare configured to perform different modulation of signals (e.g., byperforming a phase shift). Each SAW sensor may be associated with aparticular modulation and/or frequency. The different frequencies and/ormodulations of the various received RF signals may be used by thecontroller 109 to uniquely identify the specific SAW sensors thatgenerated the respective RF signals. Thus, the sensor wafer may includemany different SAW sensors, and the controller 109 can uniquelydetermine which SAW sensor generated each received RF signal based on aunique fingerprint of that RF signal. This enables the controller 109 todetermine an environmental profile across the sensor wafer 110 (e.g.,local pressures and/or temperatures across the sensor wafer 110).

FIG. 2 is a top, perspective view of a sensor device 200 (e.g., a sensorwafer) including integrated SAW sensor assemblies 210, according toaspects of the disclosure. The sensor device 200 includes a basesubstrate 202 and one or more SAW sensor assemblies 210A-D integratedinto a surface of the base substrate 202. The SAW sensor assemblies210A-D may each include an RF antenna 208A-D, matching circuitry 206A-D,and/or a SAW sensor 204A-D that are part of an integrated device.Alternatively, one or more of the SAW sensor assemblies 210A-D mayinclude integrated components of a SAW sensor 204A-D connected to adiscrete RF antenna and separate discrete matching circuitry, mayinclude an integrated SAW sensor 204A-D and matching circuitry 206A-Dconnected to a separate discrete antenna, and/or may include anintegrated SAW sensor 204A-D and antenna 208A-D connected to a separatediscrete matching circuitry. In some embodiments, a sensor wafer has atleast a layer of a piezoelectric material and includes multipleintegrated SAW sensors 204A-D formed thereon, and that optionallyincludes one or more integrated antenna 208A-D and/or integratedmatching circuitry 206A-D disposed thereon. These components aredescribed in greater detail below with reference to FIGS. 3A-B.

As shown in FIG. 2, the base substrate 202 can be a disk shapedstructure comprising a flat surface (e.g., a wafer). In otherembodiments, the base substrate 202 may be formed into other flat shapesthat can be used for transporting, depositing, and processing by aprocessing system (e.g., processing system 100 of FIG. 1). The basesubstrate 202 may be made of a conventional wafer base substrate such assilicon and can include or be partially or fully covered by apiezoelectric material, such as LiNbO₃, LiTaO₃, or La₃Ga₅SiO₁₄. In someembodiments, the base substrate may be made entirely of a piezoelectricmaterial without a conventional wafer base substrate (e.g. silicon). Insome embodiments the base substrate my include a piezoelectric substratethe includes or is composed of the piezoelectric material.

As shown in FIG. 2, the sensor device 200 includes multiple SAW sensorassemblies 210A-D integrated into and/or deposited onto the surface ofthe base substrate 202. The sensor device 200 may include one or moreSAW sensor assemblies 210A-D. While four sensor assemblies 210A-D areshown as an example, more or fewer sensor assemblies may be included insensor device 200. The SAW sensors assemblies 210 may be arranged in asensor array with each integrated SAW sensor assembly 210 measuring anenvironmental condition of a different location on the base substrate202. In some embodiments, each SAW sensor assembly is formed on a commonpiezoelectric substrate or other substrate with a piezoelectric layerformed thereon (e.g., on the same wafer). Alternatively, one or more ofthe SAW sensor assemblies may have been formed on a separatepiezoelectric substrate or substrate with a piezoelectric layer to forma discrete sensor assembly (e.g., may have been formed on a separatepiezoelectric substrate along with other SAW sensor assemblies, and thendiced and packaged to form the discrete SAW sensor assemblies). Thediscrete sensor assembly may then be mounted onto the base substrate202. In such embodiments, the base substrate 202 may or may not be apiezoelectric material. Each SAW sensor assembly 210A-D can be attachedto or disposed at a different location on the base substrate 202.

As shown in FIG. 2, the SAW sensor assemblies 210A-D each include an RFantenna 208A-D, matching circuitry 206A-D, and a SAW sensor 204A-D. TheRF antenna 208A-D, the matching circuitry 206A-D, and the SAW sensor204A-D may each include planar conductors. For example, the RF antenna208A-D, the matching circuitry 206A-D, and the SAW sensor 204A-D mayeach be formed by depositing a single conducting layer for eachconductive element (e.g., one layer for the IDT(s) and/or reflectors,one layer for the antenna, and one layer for the matching network). Insome embodiments, the RF antenna 208A-D, the matching circuitry 206A-D,and the SAW sensor 204A-D (e.g., including one or more IDT and/or one ormore reflectors) may form a single conducting layer, where depositingeach element may be performed together in a single lithography step. TheRF antenna 208A-D, the matching circuitry 206A-D, and/or the SAW sensor204A-D of a single SAW sensor assembly 120A-D may be integrated with oneanother on the base substrate 202 (or on a separate piezoelectricsubstrate or material). Additionally, in some embodiments some or all ofthe SAW sensor assemblies 120A-D (including their SAW sensors, matchingnetworks and antennas) are integrated together on the base substrate202. The RF antenna 208A-D, the matching circuitry 206A-D, and the SAWsensor 204A-D may include various materials and configurations asdiscussed in other embodiments herein.

In some embodiments, the sensor device 200 may include a protectivecoating or layer disposed above one or more of the SAW sensor assemblies210. The protective coating may include a dielectric material, which mayhave a high temperature resistance (e.g. 300-1000 Degrees Celsius)Examples of dielectric coatings that may be used include Al₂O₃, AlN,Y₂O₃, Y₃Al₅O₁₂, yttrium-based oxides, fluorides and/or oxyfluorides, andso on.

In some embodiments, the sensor device 200 includes a layer on the backside of the base substrate 202 opposite the SAW sensor assemblies 210.This layer on the back side may include or be a metal layer. The metallayer may be used to minimize interference from other signals (e.g., RFantennas 129 of FIG. 1 in other chambers) and may optionally provideincreased support for holding the sensor device 200 by a chuck (e.g., anelectrostatic chuck).

In some embodiments, the sensor device 200 may include a shieldingstructure disposed over an area of the base substrate above the SAWsensor 204, or a portion thereof. The shielding structure may include arecess above the area of the base substrate 202 to allow propagation ofSAWs across a surface of the base substrate 202. The shielding structuremay include a material with high temperature resistance and/or a highpressure resistance. In some embodiments, the material is metal, such asstainless steel, aluminum or an aluminum alloy. In some embodiments, thematerial is a ceramic, which may be a dielectric material. In someembodiments, the shielding structure is disposed across a greaterportion of the base substrate 202. For example, the shielding structuremay include a cover that completely encloses the sensor device 200.

In some embodiments, as shown in FIG. 2, the SAW sensor assemblies210A-D may be disposed on the same side (e.g., front side) of thesubstrate. However, in other embodiments, the SAW sensor assemblies may210A-D be disposed on both the front side and the back side of thesubstrate. For example, a first set of SAW sensor assemblies (which mayoperate at a first resonant frequency) may be disposed on a first sideof the base substrate 202 and a second set of SAW sensors (which mayoperate at a second resonant frequency) may be disposed on a second sideof the base substrate 202.

In some embodiments, the SAW sensor assemblies 210A-D may be located inclose proximity to one another. SAW sensor assemblies may be co-locatedor share elements (e.g., an RF antenna 208A, matching circuitry 206A,and/or SAW sensor of a first SAW sensor assembly may be a part ofanother SAW sensor assembly) in some embodiments. In one embodiment, afirst IDT may be adjacent to a second IDT. The first IDT may generate aSAW that is reflected by reflectors back to the second IDT. In oneembodiment, SAW reflectors of a SAW sensor (e.g. 204A) may be used toreflect SAWs from a second SAW sensor assembly. In another example, twoSAW sensor assemblies may include SAW sensors that may generate andpropagate SAWs across the same region of the substrate 202. In anotherexample, the SAW sensor assemblies may be formed such that the IDT ofthe SAW sensors 204 are disposed adjacent to each other and propagateSAWs in two different directions.

FIGS. 3A-B depict various embodiments of SAW sensor assemblies 300A-B,according to aspects of the disclosure. The SAW sensor assemblies 300may include an RF antenna 306A-B, matching circuitry 304A-B, and a SAWsensor 302A-B. The SAW sensor assemblies may be used, for example, onsensor device 200 of FIG. 2.

The RF antenna 306A-B may include a planar conductor or multipleconducting layers coupled together to receive and/or transmit RFsignals. As used herein, components that are coupled together may bedirectly coupled or indirectly coupled. For example, an IDT that iscoupled to an antenna may be directly coupled to the antenna or may beindirectly coupled to the antenna via a matching network that is betweenthe IDT and the antenna. The RF antenna 306A-B may operate as a filterassociated with a specific RF range. The RF antenna 306A-B may include aresonator antenna (e.g., such as a dielectric resonator antenna), afractal antenna, or some other type of antenna. RF antenna 306A-B may bea flat structure or formed to be generally flat or flush against thesurface of a substrate (e.g., may be a planar conductor). The matchingcircuitry 304A-B is coupled to the RF antenna 306A-B and the SAW sensor302A-B. The matching circuitry 304A-B may include combinations ofcircuitry components such as resistors, capacitors, and/or inductors tomatch the impedance and/or load of the RF antenna 306A-B. The matchingcircuitry 304A-B may be designed to minimize signal reflections betweenthe RF antenna 306A-B and the SAW sensor 302A-B in embodiments. Each SAWsensor 302A-B is coupled to a respective RF antenna 306A-B through arespective matching circuitry 304A-B. As shown in FIGS. 3A-B, the SAWsensor 302A-B may include an interdigitated transducer (IDT) 310A-B. TheIDT 310A-B includes two comb-shaped electrodes that are interdigitatedwith each other. The IDT 310A-B may be disposed on a piezoelectricmaterial (e.g., base substrate 202 of FIG. 2). The IDT receives anincoming signal (e.g., alternating current (AC) signal) from thematching circuitry 304 and generates an electric field in the gapsbetween the conducting digits of the electrodes based on the signal.This electric field generates a SAW on the surface of the piezoelectricmaterial.

As shown in FIG. 3A, the SAW sensor 302A may include SAW reflectors312A-B. The SAW generated by the IDT 310 propagates along the surface ofthe piezoelectric material to the SAW reflectors 312A-B. The SAWreflectors 312A-B may include strips of conducting material (e.g.,planar conductors) designed to reflect a part of the incoming SAWgenerated by the IDT 310A. These reflected portions of the SAW may bereflected back to the IDT 310A. The IDT 310A may combine the reflectedSAWs as reflected by multiple reflectors 312A-B together to generate anoscillating electric potential. The oscillating electric potential maybe sent to the RF antenna 306. The RF antenna 306 outputs an outgoing RFsignal associated with the oscillating electric potential, which may bereceived by an RF signal receiving device (e.g., RF antenna 129 of FIG.1). The oscillating electric potential generated by the IDT 310Aincludes information indicative of an environmental condition of anenvironment disposed between the IDT 310 and the SAW reflectors 312. Theenvironmental condition may be indicated by a change in frequency of theRF signal transmitted to the SAW sensor assembly 300 and the RF signalreceived in return. The signal received in return may includeinformation indicative of an environmental condition. For example, for agiven temperature or pressure the length of the piezoelectric materialwill strength or compress resulting in a change in pitch, phase, andoverall delay of the signal that may be calibrated to a specifiedtemperature or pressure. In some embodiments, the reflectors may bespatially arranged and calibrated such that a change in frequencybetween the RF signal is associated with a change in the environmentalcondition (e.g., a change in temperature or pressure).

In some embodiments the SAW reflectors 312A-B may be disposed on one ormultiple sides of the IDT 310A, as shown in FIG. 3A. The SAW reflectorsmay vary in distance between each other as well as in thickness in someembodiments. Alternatively, the SAW reflectors may have uniformthickness and/or spacing.

As shown in FIG. 3B, SAW sensor 302B includes a series of delay lines314A-C. The SAW generated by the IDT 310 propagates along the surface ofthe piezoelectric material to the delay lines 314A-C. The delay lines314A-C may include strips of conducting material (e.g., planarconductors) designed to reflect and/or delay the SAW generated by theIDT 310. The delayed and reflected SAWs return to the IDT 310 and arecombined together. The relative delay of the reflected SAWconstructively and destructively interfere with each other which resultsin an oscillating electric potential that is indicative of a measuredenvironmental condition. The oscillating electric potential may be sentto the RF antenna 306 and transmitted to another device (e.g., RFantenna 129 of FIG. 1). The oscillating electric potential includesinformation indicative of an environmental condition of an environmentbetween the IDT 310 and the delay lines 314. The environmental conditionmay be indicated by a change in frequency of the return RF signaltransmitted by the RF antenna 306 or a relative delay of the reflectedSAWs. In some embodiments, the reflectors 314A-C may be spatiallyarranged and calibrated such that a relative delay between a first setof delay lines (e.g., 314A) and a second set of delay lines (e.g., 314B)is associated with a measured environmental condition such astemperature or pressure.

In some embodiments, the SAW sensors 302A-B include a second IDT (notpictured). The first IDT 310A-B may take an incoming electric signal andgenerate a SAW associated with the incoming signal. The SAW may travelacross the piezoelectric material and be received by the second IDT. Insome embodiments, the SAW may pass through conducting elements (e.g.,delay lines 314) on the surface of the piezoelectric material beforereaching the second IDT. The second IDT may generate an oscillatingelectric potential associated with the received SAW. The oscillatingelectric potential may be transmitted through matching circuitryconnected to the second IDT to an RF antenna attached to that matchingcircuitry. The changes between the first oscillating electric potentialbased on the received RF signal and a second oscillating electricpotential generated by the IDT based on the received SAW may beindicative of a measured environmental condition. In some embodiments,multiple IDTs may share a common RF antenna and/or matching network.

In some embodiments, the RF antenna 306A-B, the matching circuitry,304A-B, and the SAW sensor 302A-B including the IDT 310A-B are allintegrated together on a common piezoelectric material. As discussedfurther in other embodiments, the SAW sensor assembly 300A-B may befully integrated into a piezoelectric material This may enable theentire SAW sensor assembly 300A-B to be fabricated together on asubstrate (e.g. a wafer) instead of pieces together in multiple assemblysteps and separate component fabrication steps. Fabricating a sensordevice having all of the components in one integrated device enables theuse of a smaller sensor device that in turn can reduce manufacturingcost, time, and reduce the required number of manufacturing steps.Additionally, fabricating a single device enables the components to becreated to be compatible with each. Also, the inefficiencies of matchingcomponent specification would be eliminated.

FIG. 4 is a flow chart of a method 400 for fabricating a SAW sensorassembly, according to aspects of the disclosure. The method 400 may beimplemented to manufacture a sensor device (e.g., sensor assembly 110 ofFIG. 1) in embodiments.

With reference to FIG. 4, at block 410, a conductive structure is formedon a substrate having at least a layer of a piezoelectric materialdisposed thereon, forming an RF antenna on the piezoelectric material.The RF antenna may correspond to any of the aforementioned RF antennas.The piezoelectric material may be any of the aforementionedpiezoelectric materials. Forming the first conductive structure mayinclude performing a photoresist deposition operation to deposit aphotoresist on the piezoelectric material, performing a patterningoperation (e.g., with a lithography device) to cure a selective portionof the photoresist, and performing an etch operation (e.g., in an etchchamber) to etch away either the cured portion or the uncured portion ofthe photoresist. A deposition process (e.g., atomic layer deposition,physical vapor deposition, chemical vapor deposition, etc.) may then beperformed (e.g., in a deposition chamber) to deposit a conductive layer(e.g., a metal layer) on the piezoelectric material and the photoresistformed thereon. A selective etch process may then be performed (e.g., inan etch chamber) to remove the photoresist and the conductive materialformed thereon, leaving behind the first conductive structure.

At block 420, a second conductive structure is formed on thepiezoelectric structure, forming matching circuitry that may have anelectrical connection to the first conductive structure that constitutesthe RF antenna (e.g., that may be coupled to the RF antenna). Thematching circuitry may correspond to the aforementioned matchingcircuitry. Forming the second conductive structure may includeperforming a photoresist deposition operation to deposit a photoresiston the piezoelectric material, performing a patterning operation (e.g.,with a lithography device) to cure a selective portion of thephotoresist, and performing an etch operation (e.g., in an etch chamber)to etch away either the cured portion or the uncured portion of thephotoresist. A deposition process (e.g., atomic layer deposition,physical vapor deposition, chemical vapor deposition, etc.) may then beperformed (e.g., in a deposition chamber) to deposit a conductive layer(e.g., a metal layer) on the piezoelectric material and the photoresistformed thereon. A selective etch process may then be performed (e.g., inan etch chamber) to remove the photoresist and the conductive materialformed thereon, leaving behind the second conductive structure. Thesecond conductive structure may be formed at the same time as the firstconductive structure. Thus, a series of operations (e.g., photoresistdeposition, lithography, etch, metal deposition, etch, etc. processes)may be performed to form both the first conductive structure and thesecond conductive structure at the same time or in parallel.

At block 430, a third conductive structure is formed on thepiezoelectric structure, forming an interdigitated transducer (IDT) onthe piezoelectric material. The IDT may be coupled to the RF antenna andthe matching circuitry. The IDT may include features and configurationsof IDTs disclosed in other embodiments of the present disclosure (e.g.,IDT 310 of FIG. 3). Forming the third conductive structure may includeperforming a photoresist deposition operation to deposit a photoresiston the piezoelectric material, performing a patterning operation (e.g.,with a lithography device) to cure a selective portion of thephotoresist, and performing an etch operation (e.g., in an etch chamber)to etch away either the cured portion or the uncured portion of thephotoresist. A deposition process (e.g., atomic layer deposition,physical vapor deposition, chemical vapor deposition, etc.) may then beperformed (e.g., in a deposition chamber) to deposit a conductive layer(e.g., a metal layer) on the piezoelectric material and the photoresistformed thereon. A selective etch process may then be performed (e.g., inan etch chamber) to remove the photoresist and the conductive materialformed thereon, leaving behind the third conductive structure. The thirdconductive structure may be formed at the same time as the first and/orsecond conductive structures. Thus, a series of operations (e.g.,photoresist deposition, lithography, etch, metal deposition, etch, etc.processes) may be performed to form the first conductive structure,second conductive structure and third conductive structure at the sametime or in parallel.

At block 440, a fourth conductive structure is formed on thepiezoelectric material, forming at least one of a a) one or more SAWreflectors or b) a second IDT electrode. The SAW reflectors and secondIDT may be separated from the IDT by a span of the piezoelectricmaterial, across which SAWs may propagate. This may cause the second IDTand/or reflectors to be communicatively coupled to the first IDT via theSAWs. The SAW reflectors may include features and configuration of SAWreflectors disclosed elsewhere in the present disclosure (e.g., SAWreflectors 312 of FIG. 3). The second IDT may include features andconfiguration of IDTs disclosed elsewhere in the present disclosure(e.g., IDT 310 of FIG. 3). Forming the fourth conductive structure mayinclude performing a photoresist deposition operation to deposit aphotoresist on the piezoelectric material, performing a patterningoperation (e.g., with a lithography device) to cure a selective portionof the photoresist, and performing an etch operation (e.g., in an etchchamber) to etch away either the cured portion or the uncured portion ofthe photoresist. A deposition process (e.g., atomic layer deposition,physical vapor deposition, chemical vapor deposition, etc.) may then beperformed (e.g., in a deposition chamber) to deposit a conductive layer(e.g., a metal layer) on the piezoelectric material and the photoresistformed thereon. A selective etch process may then be performed (e.g., inan etch chamber) to remove the photoresist and the conductive materialformed thereon, leaving behind the fourth conductive structure. Thefourth conductive structure may be formed at the same time as the first,second and/or third conductive structures. Thus, a series of operations(e.g., photoresist deposition, lithography, etch, metal deposition,etch, etc. processes) may be performed to form the first conductivestructure, second conductive structure, third conductive structure andfourth conductive structure at the same time or in parallel.

At block 450, a fifth conductive structure is optionally formed on thepiezoelectric material, forming one or more waveguides between IDTs.Forming the fifth conductive structure may include performing aphotoresist deposition operation to deposit a photoresist on thepiezoelectric material, performing a patterning operation (e.g., with alithography device) to cure a selective portion of the photoresist, andperforming an etch operation (e.g., in an etch chamber) to etch awayeither the cured portion or the uncured portion of the photoresist. Adeposition process (e.g., atomic layer deposition, physical vapordeposition, chemical vapor deposition, etc.) may then be performed(e.g., in a deposition chamber) to deposit a conductive layer (e.g., ametal layer) on the piezoelectric material and the photoresist formedthereon. A selective etch process may then be performed (e.g., in anetch chamber) to remove the photoresist and the conductive materialformed thereon, leaving behind the fifth conductive structure. The fifthconductive structure may be formed at the same time as the first,second, third and/or fourth conductive structures. Thus, a series ofoperations (e.g., photoresist deposition, lithography, etch, metaldeposition, etch, etc. processes) may be performed to form the firstconductive structure, second conductive structure, third conductivestructure, fourth conductive structure and fifth conductive structure atthe same time or in parallel.

In some embodiments, the conductive structures forming the RF antenna,the matching circuitry, the IDTs, the SAW reflectors and/or thewaveguides form a single conducting layer. The operations at block 410,420, 430, 440 and/or 450 may be performed together such that eachconductive structure is deposited together. Alternatively, one or moreof the layers may be formed separately.

In some embodiments, method 400 may further include depositing aprotective coating on the RF antenna and/or the matching circuitry. Theprotective coating may include a dielectric material, which may beplasma resistant, have a high temperature resistance and/or have a highpressure resistance. Examples of dielectric coatings that may be usedinclude Al₂O₃, AN, Y₂O₃, Y₃Al₅O₁₂, yttrium-based oxides, fluoridesand/or oxyfluorides, and so on.

In some embodiments, depositing the protective layers or protectivecoatings may be performed using atomic layer deposition, chemical vapordeposition, physical vapor deposition, or plasma enhanced versionsthereof.

FIGS. 5A-B are top, perspective views of various embodiments of SAWsensors 500 with dielectric coatings 530, 540 disposed thereon,according to aspects of the disclosure. The SAW sensor 500A-B includesan IDT 520 having two comb-shaped interdigitated electrodes disposed ona base substrate 510 having at least a layer of a piezoelectricmaterial. The SAW sensor further includes a dielectric coating 530disposed on top of the IDT 520 and base substrate 510. The SAW sensor500A-B may additionally include one or more additional IDTs and/orreflectors spaced apart from the IDT 520 on the base substrate 510. Thedielectric coating 530 may additionally coat the additional IDT(s)and/or reflectors and/or the area of the base substrate 510 between theIDT and the additional IDT(s) and/or reflectors. In embodiments in whichan integrated SAW sensor assembly also includes an RF antenna and amatching network, the RF antenna and the matching network may also becoated by the dielectric coating 530.

In some embodiments, the IDT 520 receives an electrical signal (e.g., analternating current signal) and generates a SAW across the surface ofthe piezoelectric material. The generated SAW includes a propagationvelocity and a resonant frequency. The resonant frequency of the SAWsensor can be adjusted by applying dielectric coating 530. Thedielectric coating 530 may adjust the propagation velocity of the SAWresulting in a reduced resonant frequency. The dielectric coating 530may include a thin uniform dielectric layer. Examples of dielectriccoatings that may be used include Al₂O₃, AlN, Y₂O₃, Y₃Al₅O₁₂,yttrium-based oxides, fluorides and/or oxyfluorides, and so on.

In some embodiments, a target resonant frequency can be reached bydetermining a base resonant frequency of the SAW sensor and determininga thickness and/or material to coat the surface of the SAW sensorassociated with a first frequency shift such that the base frequencywith the applied frequency shift results in the target resonantfrequency. In some embodiments, for example, as shown in in FIG. 5A, asingle dielectric layer (or dielectric layer of a first material and/orthickness) may be applied to the SAW sensor. However in otherembodiments, for example, as shown in FIG. 5B multiple dielectric layersof the same or different materials and/or thicknesses may be applied totune the resonant frequency of the IDT 520. For example, as showndielectric coating 530 is a first layer and dielectric coating 540 is asecond layer. Alternatively, a single dielectric coating (with onelayer) may be used, which may have a different thickness and/or materialthan the dielectric coating 530 used in FIG. 5A.

In some embodiments, SAW sensor 500A-B may be fabricated as according tomethod 400 of FIG. 4 and/or method 800 of FIG. 8.

In some embodiments, sensor data processing and analysis, imageprocessing algorithms, machine learning (ML) algorithms that generateone or more trained machine learning models, deep ML algorithms, and/orother signal processing algorithms for analyzing SAW sensor data can beused to determine resonant frequency shifts of a SAW sensor as a resultof applying any number of dielectric coatings of various materials andthicknesses on top of an IDT of a SAW sensor. These models, analysis,and/or algorithms can be used to calculate, predict, and evaluatecombinations of dielectric materials and thicknesses and resultingresonant frequency shifts for a given SAW sensor. Additionally, oralternatively, such techniques may be used with SAW sensor data todesign multiple SAW sensors that can operate together in close proximitywithout signals of such SAW sensors being confused. In some embodiments,training data to train a ML model may be obtained by imaging, using ascanning device or other type of sensor or camera to measure resonantfrequency shifts of SAW sensors that have previously been coated by adielectric material of a specified material and thickness.

One type of machine learning model that may be used is an artificialneural network, such as a deep neural network. Artificial neuralnetworks generally include a feature representation component with aclassifier or regression layers that map features to a desired outputspace. A convolutional neural network (CNN), for example, hosts multiplelayers of convolutional filters. Pooling is performed, andnon-linearities may be addressed, at lower layers, on top of which amulti-layer perceptron is commonly appended, mapping top layer featuresextracted by the convolutional layers to decisions (e.g. classificationoutputs). Deep learning is a class of machine learning algorithms thatuse a cascade of multiple layers of nonlinear processing units forfeature extraction and transformation. Each successive layer uses theoutput from the previous layer as input. Deep neural networks may learnin a supervised (e.g., classification) and/or unsupervised (e.g.,pattern analysis) manner. Deep neural networks include a hierarchy oflayers, where the different layers learn different levels ofrepresentations that correspond to different levels of abstraction. Indeep learning, each level learns to transform its input data into aslightly more abstract and composite representation. In an imagerecognition application, for example, the raw input may be a matrix ofpixels; the first representational layer may abstract the pixels andencode edges; the second layer may compose and encode arrangements ofedges; the third layer may encode higher level shapes (e.g., teeth,lips, gums, etc.); and the fourth layer may recognize that the imagecontains a face or define a bounding box around teeth in the image.Notably, a deep learning process can learn which features to optimallyplace in which level on its own. The “deep” in “deep learning” refers tothe number of layers through which the data is transformed. Moreprecisely, deep learning systems have a substantial credit assignmentpath (CAP) depth. The CAP is the chain of transformations from input tooutput. CAPs describe potentially causal connections between input andoutput. For a feedforward neural network, the depth of the CAPs may bethat of the network and may be the number of hidden layers plus one. Forrecurrent neural networks, in which a signal may propagate through alayer more than once, the CAP depth is potentially unlimited.

In one embodiment, a neural network is trained using a training datasetthat includes multiple data points, where each data point includes a SAWsensor configuration (e.g., including an IDT with a particular fingerarrangement and/or a particular arrangement of reflectors) and mayinclude a particular piezoelectric material and/or a dielectric coatinghaving a known material and/or thickness). Each training data point mayadditionally include or be associated with a SAW attribute, such as aSAW frequency, phase, time delay, etc. The neural network may be trainedusing the training dataset to receive an input of a SAW sensorconfiguration and target SAW attribute and to output a suggestion of adielectric coating having a particular material and/or thickness that,when deposited over the SAW sensor, will cause the SAW sensor togenerate SAWs that have the target SAW attribute.

FIG. 6 is a graph 600 depicting a frequency shift 610 in a base resonantfrequency of an SAW sensor, according to aspects of the disclosure. Afirst peak 606 shows an IDT without a dielectric coating having a firstresonant frequency. The second peak 608 shows an IDT with a dielectriccoating having a second resonant frequency. The distance between thepeaks represents a frequency shift 610 which is a result of applying thedielectric coating. The dielectric coating can be used to tune theresonant frequency. As the thickness of the dielectric coating increasesthe frequency shift 610 increases. In some embodiments, the dielectriccoating may also protect the SAW sensor from extreme environmentalconditions (e.g., from a plasma environment, from a corrosive chemicalenvironment, and so on). As shown in FIG. 6, there is a signal strengthreduction 612 resulting from the dielectric coating. The dielectriccoating may also prevent the SAW sensor from overexposure and signalsaturation from the environment in embodiments.

FIG. 7 is a top perspective view of a sensor device 700, according toaspects of the disclosure. The sensor device 700 has a base substrate702 and includes SAW sensor assemblies 704A-B disposed on the basesubstrate 702. The SAW sensor assemblies 704A-B include RF antennas 710,matching circuitry 708, and SAW sensors 706A-B. The SAW sensorassemblies 704A-B including the RF antenna 710, matching circuitry 708,and SAW sensors 706A-B may include features and configurations of SAWsensors disclosed elsewhere herein (e.g., base substrate 202 and SAWsensor assemblies 210 of FIG. 2 and 300 of FIG. 3).

As shown in FIG. 7, the SAW sensors 706A-706B may be disposed on apiezoelectric material of the base substrate 702, which may be attachedto or deposited on a base substrate 702. For example, a piezoelectricsubstrates of the SAW sensors 706A-B may be attached to a silicon wafer.In other embodiments, the SAW sensor assemblies may be fully integratedinto the base substrate 702. For example, the base substrate 702 mayinclude a common piezoelectric material and the RF antenna 710, thematching circuitry 708, and the SAW sensors 706A-B of one or more SAWsensor assemblies 704A-B may be integrated with the each other on thecommon piezoelectric material. Alternatively, one or more of the RFantenna 710 or matching circuitry 708 may be discrete devices that arenot integrated into the base substrate 702.

As shown in FIG. 7, SAW sensor 706A-B may each include an IDT disposedon a piezoelectric material and a dielectric coating covering the IDT.In some embodiments, the dielectric coating of each SAW sensor 706A-Bassembly may include the same thickness and material. In otherembodiments the thickness and/or material of the dielectric coating maybe unique for each SAW sensor assembly 704. Unique resonant frequenciesof various SAW sensor assemblies can be used to measure an environmentalcondition and map the measurement to a particular SAW sensor and thuslocation on the base substrate 702.

In some embodiments, the dielectric coating may cover a portion of theSAW sensor assembly 704 having the SAW sensor 706A-B. However, in otherembodiments, the dielectric coating may cover the entirety of each SAWsensor assembly 704 including the RF antenna 710, and the matchingcircuitry 708.

In some embodiments, each sensor assembly may include SAW sensorassemblies 704 with SAW sensors 706A-B having the same base resonantfrequency. The SAW sensors 706A-B may be tuned to generate SAWs withdifferent acoustic frequencies by generating different resonantfrequencies shifts by applying a dielectric coating with a differentthickness and/or material to each SAW sensor 7086A-B. For example, afirst saw sensor 706A may have a first dielectric coating with a firstthickness and a second SAW sensor 706B may have a second dielectriccoating with a second thickness.

In some embodiments, combinations of SAW sensor assemblies with and/orwithout dielectric coatings (not pictured) can be combined on the samebase substrate 702 as SAW sensor assemblies 704 with dielectriccoatings.

FIG. 8 is a flow chart of a method 800 for fabricating a SAW sensorassembly, according to aspects of the disclosure.

With reference to FIG. 8, at block 810, a processing system maydetermine a current RF resonant frequency range of a SAW sensor. The SAWsensor may include features and configurations of SAW sensors disclosedelsewhere herein (e.g., SAW sensor 500 of FIG. 5).

At block 820, a processing system may determine a target RF resonantfrequency range for the SAW sensor.

At block 830, a processing system may determine at least one of adielectric coating material or a dielectric coating thickness that willtune a signal propagation speed and adjust the current RF resonantfrequency range to the target RF resonant frequency range. In oneembodiment, a SAW sensor design (and optionally a target SAW attribute)is input into a trained machine learning model, which outputs asuggestion for the dielectric coating material and/or dielectric coatingthickness. In some embodiments the processing system determines acombination of dielectric materials and layers to be deposited on theSAW sensor. In some embodiments, the determined material and thicknessis dependent on SAW sensor specifications (e.g., surface area, maximumthickness, etc.).

At block 840, a processing system may deposit a dielectric coating overthe SAW sensor. The dielectric coating may have at least one of thedielectric coating material or the dielectric coating thicknessdetermined at block 830.

At block 850, a processing system may determine if the resonantfrequency is within a threshold difference of the target RF resonantfrequency. The processing system may measure the current resonantfrequency and compare the result to the target resonant frequencydetermined at block 820. If the resonant frequency is within thethreshold difference, the method 800 may complete. However, if theresonant frequency is not within the threshold difference of the targetfrequency the method returns to block 810 and repeats steps of themethod to determine and deposit another dielectric coating.

FIGS. 9A-C depict various embodiments of electrode arrangements of IDTs900A-B of a SAW sensor, according to aspects of the disclosure. The IDTs900A-C each include two comb-shaped electrodes having interlockingdigits 910A-C disposed in an arrangement on a substrate having at leasta layer of a piezoelectric material.

In some embodiments, the IDT 900A-C receives an electrical signal (e.g.,an RF signal) and generates a SAW associated with the receivedelectrical signal. In another embodiment, the IDT 900A-C receives a SAWand generates an electrical signal (e.g., an RF signal) associated withthe received SAW. In either case, the arrangement of the interlockingdigits 910A-C of the electrodes can generate a signal modulation withinany signal that passes through the IDT 900A-C.

Embodiments of the present disclosure include various arrangements ofinterlocking digits 910A-C. As shown in FIG. 9A, for example, an IDT900A may include a first arrangement of alternating interlocking digits910A. This first arrangement may result in an unmodulated signal 920Ahaving a particular resonant frequency and/or phase. As shown in FIG.9B, for example, an IDT 900B may include a second arrangement ofinterlocking digits 910B that includes at least two digits from the sameelectrode arranged adjacent to each other. This arrangement may resultin a modulated signal 920B. In some embodiments modulated signal 920Bmay include the same resonant frequency as the unmodulated signal 920Abut with a phase shift or otherwise modified signal. The pitch orspacing between the interlocking fingers may also be adjusted to createa modulated signal with an adjusted or modulated frequency, as set forthin FIG. 9C.

In some embodiments, the arrangement of the interlocking digits (e.g.,910B) may result in a signal modulation that identifies the IDT (e.g.,910B). For example, the modulated signal (e.g., 920B) includes uniquesignal modulations (e.g., phase shifts 930) that act as identifiers tofurther signal processing devices (e.g., RF antenna 129 of FIG. 1). In afurther example, the signal generated by the SAW sensor may includeinformation identifying a measurable environmental condition as well asa signal modulation that identifies that SAW sensor that transmitted thesignal comprising the information.

In some embodiments, the signal modulation generated by the arrangementof interlocking digits may result in a signal modulation comprisingphase shifts of the original signal. For example, as shown in FIG. 9B,the arrangement of interlocking digits 910B results in a signal of thesame frequency of the unmodulated signal with phase shifts 930 atvarious location across the signal. In some embodiments, the modulatedsignal includes the same frequency as the unmodulated signal.

IDTs 900A-C depicted in FIGS. 9A-C may be subsets or subsections of anIDT used in various embodiments of the present disclosure. For example,the arrangement depicted by IDT 900A may be repeated for a longer IDT.In another example, the IDT 900B depicted in FIG. 9B may include moreinterlocking digits than depicted and these digits may include variousarrangements that result in various phase and/or frequency modulations.For example, IDT 900B may be associated with phase shifting a pulse ofthe signal, but when combined with other subsections (not depicted)create a signal modulation of a signal comprised of multiple modulatedpulses resulting in a modulated signal. In some embodiments,combinations of arrangements depicted by IDT 900A and IDT 900B may becombined to have both phase shifting regions and regions withoutmodulations. For example, an IDT may comprise alternating subsectionsthat include IDT 900A and IDT 900B that result in signal modulations.Additionally, an IDT may comprise alternating subsections that includeIDT 900A, IDT 900B and/or IDT 900C that result in signal modulations.

In some embodiments, the IDTs 900A-C may be a part of a SAW sensor(e.g., SAW sensor 204 of FIG. 2) of a sensor assembly (e.g., SAW sensorassembly 210 of FIG. 2) of a sensor device (e.g., sensor device 200 ofFIG. 2). Various SAW sensor assemblies may be disposed across a basesubstrate (e.g., wafer). Each SAW sensor assembly may include a SAWsensor with an IDT having a unique arrangement of digital interlockingdigits. Each SAW sensor may measure an environmental condition andreturn the information in a signal having a signal modulationidentifying the SAW sensor assembly that transmitted the information. Itcan be appreciated that by having unique signal modulations, each sensorcan operate within overlapping or even equivalent resonant frequencyranges and still be differentiated from other sensors. For example, ameasured environmental condition can be mapped to a first region of thebase substrate because the signal transmitting the informationassociated with the environmental condition also includes a signalmodulation identifying a sensor located in the first region of the basesubstrate.

In some embodiments, the arrangement of interlocking digits may becombined with other embodiments of the present disclosure to identifythe sensor. For example, the arrangement of interlocking digits 910 maybe combined with an spatial arrangement of SAW reflectors 1004 asdiscussed in association with FIG. 10. This may result in a furthermodulated signal that uniquely identifies a SAW sensor. In anotherexample, the arrangement of interlocking digits 910 may be combined withthe application of a dielectric coating 530 as discussed in associationwith FIG. 5. This may result in a signal modulation combined with atuned frequency that uniquely identifies a SAW sensor. The combinationof these techniques can increase a density of SAW sensors that can beplaced together on a sensor wafer and still be uniquely identified.

FIGS. 10A-B depict various spatial arrangements of SAW reflectors of SAWsensors 1000A-B, according to aspects of the present disclosure. The SAWsensors 1000A-B include an IDT 1002A-B and one or more collections ofSAW reflectors 1004A-D disposed in a spatial arrangement on apiezoelectric substrate or on a substrate (e.g., a semiconductorsubstrate) with a piezoelectric layer disposed thereon. The IDT 1002A-Bis designed to receive an electrical signal and generate a SAW thatpropagates across a surface of the piezoelectric material of thepiezoelectric substrate or piezoelectric layer. The generated SAW isreflected by the SAW reflectors 1004A-D and returned to the IDT 1002A-B.The IDT 1002A-B generates a new electrical potential associated with thereflected SAW. The SAW reflectors can be spatially arranged to apply asignal modulation to the reflected SAW waves that are returning to theIDT 1002A-B.

As shown, a single IDT 1002A-B both generates a SAW based on a receivedRF signal and receives a reflection of the SAW and generates a new RFsignal therefrom. In such an embodiment, the generation of the SAW andthe receipt of the reflected SAW are offset in time, such that at time 1an RF signal is received and at time 2 a new RF signal is generated. Insome embodiments (not shown), two IDTs are disposed side-by-side oradjacent to one another. The first IDT may receive an RF signal andgenerate a SAW, and the second IDT may receive the reflected SAW andgenerate a new RF signal. In such a configuration, the first IDT andsecond IDT may operate in parallel. Thus, the second IDT may output thenew RF signal while the first IDT is receiving the incoming RF signal.

Embodiments of the present disclosure include various spatialarrangements of SAW reflectors 1004A-D. For example, as shown in SAWreflectors 1004A-B, a SAW sensor may include a collection of SAWreflectors that are uniformly distributed. In another example, a SAWsensor may include a collection of SAW reflectors that are not uniformlydistributed and that may be uniquely spaced. In another example, asshown in SAW reflectors 1004C-D, a SAW sensor may include one or morecollection of SAW reflectors that are grouped together. In anotherexample, as shown in SAW reflectors 1004D, a SAW sensor may include oneor more collection of SAW reflectors that are grouped with diversespacing.

In some embodiments, the spatial arrangement of SAW reflectors 1004A-Dresults in a signal modulation that identifies the SAW sensor. Forexample, each of the previously described examples depicted in FIGS.10A-B may result in signal modulations that are unique to each SAWsensor. For example, the signal modulation may result in phase changes,frequency changes, and/or signal delays as a result of the constructiveand deconstructive interference of the reflected SAWs when returning tothe IDT 1002A-B.

For example, the spacing 1010A-D between groups of SAW reflectors mayresult in unique signal modulations. For example, in FIG. 10B SAWreflectors 1004C are divided into a first group of reflectors 1009A anda second group of reflectors 1009B, and SAW reflectors 1004D are dividedinto a first group of reflectors 1009C and a second group of reflectors1009D. All of the reflectors in the first groups 1009A, 1009C have afirst pitch or spacing, and all of the reflectors in the second groups1009B, 1009D also have the first pitch or spacing. The first pitch orspacing may be, for example, approximately a spacing of one wavelengthfor a SAW. First group 1009A may be separated from second group 1009B bya gap or space 1010D, which may not be a full wavelength of the SAW.Similarly, first group 1009C may be separated from second group 1009D bythe gap or space 1010D. In embodiments, the gap or space 1010D may havea length that is a quarter wavelength, a half wavelength, three quartersof a wavelength, one and a quarter wavelength, one and a halfwavelength, one and three quarters wavelength, two and a quarterwavelength, two and a half wavelength, two and three quarterswavelength, and so on. In a further example, the spatial distribution ofthe SAW reflectors 1004A-D may include half and/or quarter wavelengthspacing between SAW reflectors. In some embodiments, SAW reflectors arearranged in groups, where a first group of SAW reflectors may be offsetfrom a second group of SAW reflectors by, for example, a half wavelengthor a quarter wavelength. In one embodiment, each SAW reflector of thefirst group of SAW reflectors is spaced from one or more nearest SAWreflector of the group by a spacing, which may correspond to thewavelength of the SAW. Additionally, each SAW reflector of the secondgroup of SAW reflectors may be spaced from one or more nearest SAWreflector from that group by the spacing, which may correspond to thewavelength of the SAW. In some embodiments, combinations ofhalf-wavelength, quarter-wavelength and/or full wavelength spacing maybe used to generate unique signal modulation that may identify the SAWsensor 1000A-B In some embodiments, the SAW sensors 1000A-B may be apart of a sensor assembly (e.g., SAW sensor assembly 210 of FIG. 2) of asensor device (e.g., sensor device 200 of FIG. 2). Various SAW sensorassemblies may be disposed across a base substrate (e.g., wafer) eachincluding a SAW sensor with an IDT and a collection of SAW reflectorsdisposed in a unique spatial arrangement. Each SAW sensor may measure anenvironmental condition and return the information in a signal having asignal modulation that identifies the SAW sensor assembly thattransmitted the information. It can be appreciated that by having uniquesignal modulations, each sensor can operate within overlapping or evenequivalent resonant frequency ranges and still be differentiated fromother sensors. For example, a measured environmental condition can bemapped to a first region of the base substrate because the signaltransmitting the information associated with the environmental conditionalso includes a signal modulation identifying a sensor located in thefirst region of the base substrate.

In some embodiments, the spatial arrangement of SAW reflectors may becombined with other embodiments of the present disclosure to identify aSAW sensor. For example, a unique spatial arrangement of SAW reflectors1004A-D of a SAW sensor may be combined with a unique arrangement ofinterlocking digits 910 of the IDT as discussed in association with FIG.9. This may result in a further modulated signal that uniquelyidentifies a SAW sensor. In another example, a unique spatialarrangement of SAW reflectors 1004 may be combined with an applieddielectric coating 530 as discussed in association with FIG. 5. This mayresult in a signal modulation combined with a tuned frequency thatuniquely identifies a SAW sensor.

FIG. 11-14 are top, perspective views of various embodiments of sensordevices 1100-1400, according to aspects of the disclosure. The sensordevices include a substrate 1102-1402 having at least a layer of apiezoelectric material (e.g., a piezoelectric substrate or asemiconductor substrate with a piezoelectric layer disposed thereon) andSAW sensor assemblies 1104-1404 and 1108-1208 that are designed toreceive and/or transmit RF signals associated with measuring anenvironmental condition of an environment using SAWs 1106-1406. Thesensor assemblies may include RF antennas, matching circuitry, and SAWsensors having IDTs. The sensor assemblies may include features andconfigurations of SAW sensor assemblies disclosed elsewhere herein(e.g., sensor device 200). The following exemplary embodiments disclosevarious configurations of transmitting SAWs between multiple sensorassemblies to measure an environmental condition in a region on thesurface of the piezoelectric material between the multiple sensorassemblies.

In some embodiments, for example, as shown in FIG. 11, the sensor device1100 may include a first SAW sensor assembly 1104A designed to receiveincoming RF signals and generate a SAW 1106A that propagates across thesurface of the substrate 1102, which may be a piezoelectric substrate ora substrate with a piezoelectric layer disposed thereon. The SAW 1106 isreceived by a second SAW sensor assemblies 1108A designed to generate anelectrical potential associated with the received SAW 1106A and outputan outgoing RF signal associated with the electrical potential, wherethe outgoing RF signal output includes information indicative of anenvironmental condition of an environment between the first SAW sensorassembly 1104A and second SAW sensor assembly 1108A. In someembodiments, a waveguide is disposed between the first SAW sensorassembly 1104A and the second SAW sensor assembly 1108A. The waveguidecan maintain the SAW that propagates between first SAW sensor assembly1104A and second SAW sensor assembly 1108A. In some embodiments, thefirst SAW sensor assembly 1104A and second SAW sensor assembly 1108A arepart of a single integrated device. In some embodiments, matchingnetworks and/or antennas of the SAW sensor assemblies 1104A, 1108A arenot part of the integrated device, and are instead discrete components.In some embodiments, a waveguide disposed between the first SAW sensorassembly 1104A and second SAW sensor assembly 1108A is part of anintegrated device along with the first and/or second SAW sensorassemblies 1104A, 1108A. In a further embodiment, the sensor device mayinclude a first set of SAW sensor assemblies 1104 that each generateSAWs 1106 that are received by a second set of SAW sensor assemblies1108. Each of the SAW sensor assemblies may be part of a singleintegrated device in embodiments. In some embodiments, waveguides aredisposed between one or more respective pairs of first SAW sensorassemblies 1104A-D and second SAW sensor assemblies 1108A-D.

In some embodiments, for example, as shown in FIG. 12, the sensor device1200 may include a set of SAW generating sensor assemblies 1204 that aredesigned to receive incoming RF signals and generate SAWs 1206 thatpropagate across the surface of the substrate 1202, which may be apiezoelectric substrate or a substrate with a piezoelectric layer. Thesensor device 1200 may also include a SAW receiving sensor assembly 1208that is designed to receive the SAWs 1206 generated by the set of SAWgenerating sensor assemblies 1204. The SAW receiving sensor assembly1208 may be designed to generate an oscillating electric potentialassociated with each of the SAWs 1206 generated by the SAW generatingsensor assemblies 1204. The SAW receiving sensor assembly 1208 outputsan outgoing RF signal in accordance with each oscillating electricpotential, where each RF signal includes information indicative of anenvironmental condition of an environment disposed between the SAWreceiving sensor assembly 1208 and the associated SAW generating sensorassembly (e.g., 1204A). A first waveguide may be disposed between SAWgenerating sensor assembly 1208 and first SAW sensor assembly 1204A, anda second waveguide may be disposed between SAW generating assembly 1208and second SAW sensor assembly 1204B in some embodiments. In someembodiments, the first SAW sensor assembly 1204A, second SAW sensorassembly 1204B and SAW receiving sensor assembly 1208 are part of asingle integrated device. In some embodiments, matching networks and/orantennas of the SAW sensor assemblies 1204A, 1204B, 1208 are not part ofthe integrated device, and are instead discrete components. In someembodiments, a first waveguide disposed between the first SAW sensorassembly 1204A and SAW receiving sensor assembly 1208 and a secondwaveguide disposed between the second SAW sensor assembly 1204B and SAWreceiving sensor assembly 1208 is part of an integrated device alongwith the first SAW sensor assembly 1204A, second SAW sensor assembly1204B and/or SAW receiving sensor assembly 1208. In a furtherembodiment, the sensor device 1200 may include multiple sets of SAWgenerating sensor assemblies (e.g., 1204) and multiple SAW receivingsensor assemblies (e.g., 1208) to receive SAWs (e.g., 1206) generated byeach set of SAW generating sensor assembles.

In some embodiments, for example, as shown in FIG. 13, the sensor device1300 may include two sensor assemblies 1304A and 1304B each disposed ona piezoelectric substrate 1302 (or substrate with a piezoelectric layerdisposed thereon). Each sensor assembly 1304A and 1304B may receive anincoming RF signal and generate a SAW 1306 associated with the receivedincoming RF signal. The SAW 1306 generated by each signal is received bythe other sensor assembly. For example, a SAW 1306 generated by a firstsensor assembly 1304A is received by a second sensor assembly 1304B anda SAW 1306 generated by the second sensor assembly 1304B is received bythe first sensor assembly 1304A. Each sensor assembly 1304 may generatean oscillating electric potential associated with the corresponding SAW1306 received by each sensor assembly 1304. Each sensor assembly 1304may output an outgoing RF signal in accordance with each oscillatingelectric potential, where each outgoing RF signal includes informationindicative of an environmental condition of an environment disposedbetween the two sensor assemblies 1304A and 1304B. In a furtherembodiment, a processing system (e.g., processing system 100 of FIG. 1)may coordinate sending incoming RF signals such that the sensorassemblies alternate roles of SAW generation and oscillating electricpotential generation. In a different embodiment, a processing system maycoordinate sending incoming RF signals such that each sensor assembly1304 generates SAWs synchronous with the other sensor assembly 1304. Ina further embodiment, the sensor device 1300 may include multiple pairsof sensor that operate in accordance with previously described exemplaryembodiments detailing sensor assembly 1304A and 1304B.

In some embodiments, a waveguide is disposed between the first SAWsensor assembly 1304A and the second SAW sensor assembly 1304B. In someembodiments, the first SAW sensor assembly 1304A and second SAW sensorassembly 1304B are part of a single integrated device. In someembodiments, matching networks and/or antennas of the SAW sensorassemblies 1304A-B are not part of the integrated device, and areinstead discrete components. In some embodiments, a waveguide disposedbetween the first SAW sensor assembly 1304A and second SAW sensorassembly 1304B is part of an integrated device along with the firstand/or second SAW sensor assemblies 1304A, 1304B.

In some embodiments, as shown in FIG. 14, the sensor device 1400 mayinclude multiple sensor assemblies 1404 disposed on a surface of asubstrate 1402 having at least a layer of a piezoelectric material. Thesensor device 1400 may include a SAW sensor assembly 1404A that isdesigned to receive an incoming RF signal and generate SAWs 1406 thatare to be received by multiple SAW sensor assemblies 1404B, 1404C, and1404D. The sensor device 1400 may include a SAW sensor assembly 1404Bthat is designed to receive a SAW 1406A from another SAW sensor assembly1404A and generate an oscillating electric potential associated with theSAW and output an incoming RF signal associated with the generatedoscillating electric potential. SAW sensor assembly 1404B may also bedesigned to generate a SAW 1408 responsive to receiving an incoming RFsignal. The sensor device may further include a SAW sensor assembly1404C that is designed to receive SAWs 1408 and 1406B from multiple SAWsensor assemblies 1404A and 1404B. SAW sensor assembly 1404C maygenerate oscillating electric potentials for each of the received SAWsand output outgoing RF signals associated with each of the generatedoscillating electric potentials. SAW sensor assembly 1404C may also bedesigned to generate a SAW 1410 responsive to receiving an incoming RFsignal. The sensor device may further include a SAW sensor assembly1404D that is designed to receive SAWs 1410 and 1406C from multiple SAWsensor assemblies 1404C and 1404A. SAW sensor assembly 1404D maygenerate electric potentials for each of the received SAWs and outputoutgoing RF signals associated with each of the generated oscillatingelectric potentials.

In some embodiments, one or more of the SAW sensor assemblies 1404A-Dare part of a same integrated device. In some embodiments, waveguidesare disposed between one or more of the SAW sensor assemblies 1404A-D,such as between SAW sensor assembly 1404A and SAW sensor assembly 1404Dand/or between SAW sensor assembly 1404A and SAW sensor assembly 1404C.The waveguides may be part of an integrated device with the one or moreSAW sensor assemblies in embodiments. For example, the waveguides may beplanar conductors formed on the piezoelectric material on which the SAWsensor assemblies are formed.

In some embodiments, combinations of embodiments shown in FIGS. 11-14are used. For example, sensor assemblies 1104, 1108, 1204, 1208, 1304,and 1404 can be used in any combination with each other on the surfaceof a piezoelectric substrate to measure environmental conditions atdifferent regions across the surface of a piezoelectric substrateresponsive to receiving incoming RF signals.

The preceding description sets forth numerous specific details such asexamples of specific systems, components, methods, and so forth, inorder to provide a good understanding of several embodiments of thepresent disclosure. It will be apparent to one skilled in the art,however, that at least some embodiments of the present disclosure may bepracticed without these specific details. In other instances, well-knowncomponents or methods are not described in detail or are presented insimple block diagram format in order to avoid unnecessarily obscuringthe present disclosure. Thus, the specific details set forth are merelyexemplary. Particular implementations may vary from these exemplarydetails and still be contemplated to be within the scope of the presentdisclosure.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment” in various places throughout thisspecification are not necessarily all referring to the same embodiment.In addition, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.” When the term “about” or “approximately” is usedherein, this is intended to mean that the nominal value presented isprecise within ±10%.

Although the operations of the methods herein are shown and described ina particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operation may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be in an intermittentand/or alternating manner. In one embodiment, multiple metal bondingoperations are performed as a single step.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. The scope of the disclosure should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

What is claimed is:
 1. A sensor assembly comprising: a first surfaceacoustic wave (SAW) sensor adapted to measure a first environmentalcondition responsive to receiving a first RF signal, the first SAWsensor comprising: a first substrate comprising at least a layer of apiezoelectric material; and a first interdigitated transducer (IDT)formed on the piezoelectric material, the first IDT comprising twocomb-shaped electrodes comprising interlocking conducting digits in afirst arrangement, wherein the interlocking conducting digits in thefirst arrangement generate a first signal modulation of the first RFsignal received by the first IDT, wherein the first signal modulationidentifies the first SAW sensor.
 2. The sensor assembly of claim 1,further comprising: a second SAW sensor adapted to measure the firstenvironmental condition responsive to receiving the first RF signal or asecond RF signal, the second SAW sensor comprising: a second IDT formedon the piezoelectric material of the first substrate or on a secondsubstrate, the second IDT comprising two comb-shaped electrodescomprising interlocking conducting digits in a second arrangement,wherein the interlocking conducting digits in the second arrangementgenerate a second signal modulation of the first RF signal or the secondRF signal received by the second IDT, wherein the second signalmodulation identifies the second SAW sensor.
 3. The sensor assembly ofclaim 2, wherein the second arrangement of the second IDT comprises atleast two digits from the same comb-shaped electrode of the twocomb-shaped electrodes arranged adjacent to each other.
 4. The sensorassembly of claim 1, wherein the first SAW sensor further comprises afirst plurality of SAW reflectors communicatively coupled to the firstIDT and formed on the piezoelectric material, wherein the firstplurality of SAW reflectors have a first spatial arrangement that causesthe first SAW reflected from the first plurality of SAW reflectors andback to the first IDT to have a second signal modulation that, whencombined with the first signal modulation, identifies the first SAWsensor.
 5. The sensor assembly of claim 4, further comprising: a secondSAW sensor adapted to measure the first environmental conditionresponsive to receiving the first RF signal or a second RF signal, thesecond SAW sensor comprising: a second IDT formed on the piezoelectricmaterial of the first substrate or on a second substrate; and a secondplurality of SAW reflectors communicatively coupled to the second IDTand formed on the piezoelectric material, wherein the second pluralityof SAW reflectors have a second spatial arrangement that causes thesecond SAW reflected from the second plurality of SAW reflectors andback to the second IDT to have a second signal modulation thatidentifies the second SAW sensor.
 6. The sensor assembly of claim 1,wherein the first arrangement generates the first signal modulation byphase shifting at least a portion of the first RF signal.
 7. The sensorassembly of claim 1, wherein the first arrangement generates the firstsignal modulation by frequency shifting at least a portion of the firstRF signal.
 8. The sensor assembly of claim 1, wherein the first SAWsensor further comprises: a first dielectric coating of at least one ofa first thickness or a first material disposed on the first IDT,wherein: the first IDT comprises a first base resonant frequency; atleast one of the first thickness or the first material is associatedwith a first shift in the first base resonant frequency; and the firstIDT with the first dielectric coating has a first adjusted resonantfrequency.
 9. The sensor assembly of claim 8, further comprising: asecond SAW sensor adapted to measure the first environmental conditionresponsive to receiving the first RF signal or a second RF signal, thesecond SAW sensor comprising a second IDT formed on the piezoelectricmaterial of the first substrate or on a second substrate; and a seconddielectric coating of at least one of a second thickness or a secondmaterial disposed on the second IDT, wherein: the second IDT comprisesthe first base resonant frequency or a second base resonant frequency;at least one of the second thickness or the second material isassociated with a second shift in the second base resonant frequency;and the second IDT with the second dielectric coating has a secondadjusted resonant frequency.
 10. A sensor assembly comprising: a firstsurface acoustic wave (SAW) sensor disposed on a substrate comprising atleast a layer of a piezoelectric material, wherein the first SAW sensoris adapted to measure an environmental condition of an environmentresponsive to receiving a first RF signal, the first SAW sensorcomprising: a first interdigitated transducer (IDT) formed on a firstregion of the piezoelectric material, the first IDT to generate a firstSAW based on the environmental condition responsive to receiving thefirst RF signal; and a first plurality of SAW reflectors communicativelycoupled to the first IDT and formed on a second region of thepiezoelectric substrate; wherein the first plurality of SAW reflectorshave a first spatial arrangement that causes the first SAW reflectedfrom the first plurality of SAW reflectors and back to the first IDT tohave a first signal modulation that identifies the first SAW sensor. 11.The sensor assembly of claim 10, further comprising: a second SAW sensordisposed on the piezoelectric material, wherein the second SAW sensor isadapted to measure the environmental condition of the environmentresponsive to receiving the first RF signal or a second RF signal, thesecond SAW sensor comprising: a second IDT formed on a third region ofthe piezoelectric material, the second IDT to generate a second SAWbased on the environmental condition responsive to receiving the firstRF signal or the second RF signal; and a second plurality of SAWreflectors communicatively coupled to the second IDT and formed on afourth region of the piezoelectric material; wherein the secondplurality of SAW reflectors have a second spatial arrangement thatcauses the second SAW reflected from the second plurality of SAWreflectors and back to the second IDT to have a second signal modulationthat identifies the second SAW sensor.
 12. The sensor assembly of claim10, wherein the first spatial arrangement of SAW reflectors comprises aspacing between a first SAW reflector of the plurality of SAW reflectorsand a second SAW reflector of the plurality of SAW reflectors such thata first reflected SAW from the first SAW reflector and a secondreflected SAW from the second SAW reflector constructively interferewith each other.
 13. The sensor assembly of claim 10, wherein the firstspatial arrangement of SAW reflectors generates the first signalmodulation by phase shifting at least a portion of the first RF signal.14. The sensor assembly of claim 10, wherein the first spatialarrangement of SAW reflectors comprise at least two reflectors separatedby a quarter wavelength or a half wavelength of the first SAW.
 15. Thesensor assembly of claim 10, wherein the first SAW sensor furthercomprises: a first dielectric coating of at least one of a firstthickness or a first material disposed on the first IDT, wherein: thefirst IDT comprises a first base resonant frequency; at least one of thefirst thickness or the first material is associated with a first shiftin the first base resonant frequency; and the first IDT with the firstdielectric coating has a first adjusted resonant frequency.
 16. Thesensor assembly of claim 15, wherein the first SAW sensor furthercomprises: a second interdigitated transducer (IDT) formed on a thirdregion of the piezoelectric material; and a second dielectric coating ofat least one of a second thickness or a second material disposed on thesecond IDT, wherein: the second IDT comprises a second base resonantfrequency; at least one of the second thickness or the second materialis associated with a second shift in the second base resonant frequency;and the second IDT with the second dielectric coating has a secondadjusted resonant frequency.
 17. A sensor assembly comprising: a firstsurface acoustic wave (SAW) sensor adapted to measure a firstenvironmental condition responsive to receiving a first RF signal, thefirst SAW sensor comprising: a first interdigitated transducer (IDT)formed on a substrate comprising at least a layer of a piezoelectricmaterial, the first IDT comprising a first base resonant frequency; anda first dielectric coating of at least one of a first thickness or afirst material disposed on the first IDT, wherein at least one of thefirst thickness or the first material is associated with a first shiftin the first base resonant frequency, wherein the first IDT with thefirst dielectric coating has a first adjusted resonant frequency. 18.The sensor assembly of claim 17, further comprising: a second SAW sensoradapted to measure the first environmental condition responsive toreceiving a second RF signal, the second SAW sensor comprising: a secondinterdigitated transducer (IDT) formed on the substrate or on a secondsubstrate, the second IDT comprising the first base resonant frequencyor a second base resonant frequency; and a second dielectric coating ofat least one of a second thickness or a second material disposed on thesecond IDT, wherein at least one of the second thickness or the secondmaterial is associated with a second shift in the first base resonantfrequency or the second base resonant frequency, wherein the second IDTwith the second dielectric coating has a second adjusted resonantfrequency.
 19. The sensor assembly of claim 18, wherein the firstadjusted resonant frequency is different than the second adjustedresonant frequency such that the first SAW sensor with the firstdielectric coating operates at a different resonant frequency than thesecond SAW sensor with the second dielectric coating.
 20. A systemcomprising: a processing chamber; one or more RF antenna to transmit afirst RF signal within the processing chamber and to receive a second RFsignal propagating from within the processing chamber; and a sensorwafer disposed within the processing chamber, the sensor wafercomprising: at least a layer of a piezoelectric material; and a firstintegrated sensor assembly comprising: a first surface acoustic wave(SAW) sensor disposed on at least the layer of the piezoelectricmaterial, wherein the first SAW sensor is adapted to measure a firstenvironmental condition of an environment located within the processingchamber responsive to receiving the first RF signal and to output thesecond RF signal having data associated with the measured environmentalcondition, wherein the first SAW sensor comprises: a firstinterdigitated transducer (IDT) formed on a first region of thepiezoelectric material, the first IDT comprising two comb-shapedelectrodes comprising interlocking conducting digits disposed in a firstspatial arrangement; and a first plurality of SAW reflectorscommunicatively coupled to the first IDT and formed on a second regionof the piezoelectric substrate, wherein the first plurality of SAWreflectors have a second spatial arrangement, wherein the interlockingconducting digits in the first spatial arrangement or the firstplurality of SAW reflectors in the second spatial arrangement generate afirst signal modulation of the first and second RF signals, wherein thefirst signal modulation identifies the first SAW sensor.